Health enthusiasts all over the country can breathe a collective sigh of relief. According to the results of a new study, the number of Americans getting sufficient exercise has increased steadily over the last few years. But don’t break out the celebratory ice cream just yet — unfortunately, that same study also found the number of obese Americans continues to climb.
But it’s too early to conclude that physical activity has nothing to do with weight management. Here’s why the link between exercise and weight loss is more complicated than we might want to believe.
What’s the Deal?
The study, led by the University of Washington’s Institute for Health Metrics and Evaluation (IHME), looked at statistics that included the number of Americans who reported sufficient physical activity between 2001 and 2009 in addition to obesity rates during that same time period. (The researchers defined “sufficient physical activity” as the American Heart Association's recommendation of 150 minutes of moderate physical activity, 75 minutes of vigorous physical activity, or the equivalent combination each week.)
According to their results, the number of people getting the recommended amount of exercise increased significantly between 2001 and 2009, and the increase was greater for females than for males. In the most active U.S. counties, the number of people exercising sufficiently rose by up to 17 percent for males and 18 percent for females. At the same time, obesity rates continued to rise throughout the country, and only nine U.S. counties saw (small) decreases in obesity. Time to cancel our gym memberships and toss out those skinny jeans — right?
Why It Matters
The conclusion here isn’t that exercise has no impact on weight loss or (more importantly) on overall health — there’s simply too much evidence pointing to the health benefits of working out. In fact, we can’t really come to any definite conclusion based on this recent study’s findings. We can only speculate some potential reasons why increasing rates of physical activity seem to have had a limited effect on obesity trends.
One idea is that with increased physical activity, people are also consuming more calories. Recent research suggests exercise doesn’t always lead to weight loss, and some scientists say that’s because people tend to eat more when they work out Why do individuals not lose more weight from an exercise intervention at a defined dose? An energy balance analysis. Thomas, D.M., Bouchard, C., Church, T., et al. Center for Quantitative Obesity Research, Montclair State University, Montclair, NJ, USA. Obesity Reviews 2012 Oct;13(10):835-47. . Other studies have found that when it comes to appetite, exercise intensity is key: While moderate exercise appears to curb appetite, high-intensity exercise may motivate us to eat more Effects of exercise on gut peptides, energy intake and appetite. Martins, C., Morgan, L.M., Bloom, S.R., et al. School of Biomedical and Molecular Sciences, University of Surrey, Guildford, UK. Journal of Endocrinology 2007 May;193(2):251-8. Effects of exercise intesntiy on food intake and appetite in women. Pomerleau, M., Imbeault, P., Parker, T., et al. School of Human Kinetics, University of Ottawa, Ontario, Canada. Amerian Jounra of Clinical Nutrition 2004 Nov;80(5):1230-6. . Women in particular are especially likely to eat more after exercising, possibly because of a biological mechanism designed to maintain levels of body fat — and a key finding from the IHME study is that women showed a greater increase in physical activity than men Effects of exercise on energy-regulating hormones and appetite in men and women. Hagobian, T.A., Sharoff, C.G., Stephens, B.R., et al. University of Massachusetts Amherst, Energy Metabolism Laboratory, Department of Kinesiology, Amherst, MA, USA. American Journal of Physiology2009 Feb;29692):R233-42. Then there’s the issue of what kinds of food people eat — 30 to 60 minutes of physical activity each day isn’t going to combat a steady diet of fast and processed foods.
What this study may point to is the crucial role of diet and nutrition in any wellness routine. In fact, new research suggests that people who think exercise is the most important factor in weight loss have higher BMIs than people who think diet is more significant Lay Theories of Obesity Predict Actual Body Mass. McFerran, B., Mukhopadhyay, A. Ross School of Business, University of Michigan. Psychological Science 2013 Jun 5. Epub ahead of print. .
Another potential reason for the IHME findings is the fact that the people exercising more might not have been the same people getting heavier. The study didn’t look at obesity or physical activity in individuals, but instead gathered averages from different U.S. counties.
The only thing we can say for certain is that these study findings are no reason to quit working out. Physical activity is an important part of a healthy lifestyle for so many reasons — it boosts heart health, lowers blood pressure, helps beat stress, and may help reduce anxiety and depression, all factors that arguably matter more than the number on the scale. Those looking to lose weight should note that exercise alone might not do the trick, unless it’s coupled with healthy eating habits. It might also be important to be aware of how much we eat on days that we work out, since exercise might increase appetite in some people. Ultimately, these study results are only proof that researchers still have a lot of work to do when it comes to figuring out how physical activity affects our general health.
Do you find exercise helps you manage your weight? Let us know in the comments below or tweet the author at @ShanaDLebowitz.